Just wanted to add my 2 cents worth. I like to put either thick cardboard or hardboard, the brown stuff, luan plywood is good also, over the speaker grill and across the back. Office max has strapping kits for about $6.00 that you can use to secure this aroung the amp. Wrap with small bubble wrap, then large bubble wrap.
Get a box about two inches larger then the amp dimensions, and close the flaps on the bottom. Try to make it perfectly square as that will help provide structural integrity to the box. FWIW, I use 3M Super 77 spray adhesive to glue the top and bottom flaps of the box, just for a little extra strength. Then using strapping tape, I like 3M brand, put one strip across the box 90 degrees to the seam of the flaps. Be sure to put about 3 to 4 inches of tape on the side. Then place tape across the seam of the flaps. Now go along the edge of the box where the side of the flaps are and place a strip across the length of the box, corner to corner.
Before you set the amp in, place some peanuts on the bottom. at least 2 to 2 inches.Set the amp inside, being carefull not to pop the side seam on the box. Take a bag of peanuts and shake them into the box. Bending the sides out slightly to allow peanuts to fill all the spaces between the wrap and the box sides. Place enough peanuts on the top of the amp so that when you close the top flaps you will have to press the down a little. If the flaps can be pushed down you need more packing material. This will insure that the amp will not move around. Now, close the top flaps the same as you did the bottom.
Get a second box that is at least 2 or more inches larger in all dimensions. Follow the same procedure making sure the inner box cannot move. You can expect to spend some money doing this. I packed a Blue Angel that is listed on this board in the same manner, and I spent about $60.00 in materials, and several hours of time. If you had it packed it would probably be at least that much if not more.
This is a lot of work, but you will find it will avoid many problems down the road.
Cheers,
Ivabiggun